1. Field of the Invention
The present invention relates to a loudspeaker, and more particularly to a panel speaker with a wide free space in various applications such as a thin panel type, a wall mounted type, a picture stand type, and a vehicle mounted type.
2. Description of the Related Art
A conventional panel speaker is provided with an acoustic vibrating plate used as a panel, which can emit sounds when being driven by a vibration driver. Such a panel speaker is known in Japanese Patent Laid Open Patent Application (JP-A-Showa 58-210800), as shown in FIG. 1. In this conventional example, a vibration driver 2 is mounted in substantially the center of an acoustic vibrating plate 1 to apply vibration to the acoustic vibrating plate in a thickness direction of the vibrating plate 1.
FIGS. 5 and 6 illustrate profiles of simulation of the acoustic vibrating plate 1 when the center of the acoustic vibrating plate 1 is driven by the vibration driver 2 at frequencies of 5 kHz and 15 kHz, respectively. In the figures, arrows indicate the direction of vibration applied by the vibration driver 2, and the amplitude of vibration of the acoustic vibrating plate 1 is exaggerated.
Also, another conventional panel speaker is disclosed in Japanese Patent Laid Open Patent Application (JP-A-Heisei 4-150298). In this reference, a single vibration driver is mounted on substantially the center of the acoustic vibrating plate, or a plurality of vibration drivers are mounted substantially in symmetry with respect to the center of the acoustic vibrating plate. In addition, the thin panel speaker is used for a picture frame. As the panel speaker is assembled to function as a hold-down plate at the back side of a picture stand or a picture frame, its speaker system will be provided without reducing the interior space of a room.
However, the vibration driver mounted on substantially the center of the acoustic vibrating plate may yet occupy a sizable space, and preventing any instrument using the panel speaker from being down-sized.
The panel speaker has a thickness which is a sum of the thickness of the acoustic vibrating plate and the thickness of the vibration driver. This will require the panel speaker having the foregoing structure to put unfavorably in a wider space.
Consider a case where a panel speaker is stored to address in the direction shown by the arrow 111, as shown in FIGS. 2A and 2B. An acoustic vibrating plate 1 could be seated in a space equal to the thickness 19 by the width 18 of the acoustic vibrating plate 1. However, in practice, a vibration driver 2 is mounted on substantially the center of the acoustic vibrating plate 1. Therefore, there is additionally required a space defined by the thickness 29 of the vibration driver 2 and a width 27 from the edge of the acoustic vibrating plate 1 to the edge of the vibration driver 2 on the back side. In this case, along the widthwise direction, a size defined by the width 27xe2x80x2 from the edge of the acoustic vibrating plate 1 to the vibration driver 2 and the thickness 29 of the vibration driver 2 is a waste space.
Also, as shown in FIG. 3, if the two panel speakers are stored side by side, the thickness 209 required for the storage is equal to a sum of the thickness 109 of the panel speaker 100 composed of the acoustic vibrating plate 1 and the vibration driver 2 and the thickness 109xe2x80x2 of a second panel speaker 100xe2x80x2 composed of an acoustic vibrating plate 1xe2x80x2 and a vibration driver 2xe2x80x2. More specifically, the overall thickness required for the storage is two times of a sum of the acoustic vibrating plate and the vibration driver, resulting in increase of the waste space.
FIG. 4 shows an attempt for reducing the overall thickness, in which the vibration drivers 2 and 2xe2x80x2 of the panel speakers 100 and 100xe2x80x2 are prevented from being overlapped each other. Although the overall thickness 209 is reduced by the thickness of one vibration driver as compared with the above panel speaker shown in FIG. 3. However, the overall height 110 is increased. This also fails to demonstrate the advantage of the thin-type panel speakers.
In a conventional speaker structure where the vibration driver is mounted at substantially the center of the acoustic vibrating plate, the acoustic vibrating plate is commonly made of an opaque material for shielding the vibration driver from view. Accordingly, the conventional panel speaker structure will be restrictive in the application and the down-sizing of any instrument using the conventional panel speaker will be difficult.
In conjunction with the above description, a panel type speaker is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 2-170795). In this reference, the panel type speaker is composed of a thin plate section and an electric-signal-to-vibration converter. A paint and photograph can be attached to a front plane of the thin plate section. A connection section is provided at a back plane to receive vibration. The converter is connected to the thin plate section to emit the vibration toward the thin plate section.
Also, a panel speaker is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 4-287500). In this reference, a concave portion (14) is formed in an acoustic vibration plate (1) in correspondence to an amplifier section (15). The amplifier section (15) is fit to the concave portion (14) and is fixed to a frame (7a).
Also, a panel speaker with a waterproof function is disclosed in Japanese Patent No. 2,570,679. In this reference, a gap section is formed in resin sheet fitting section at the front and back planes of a resin frame panel in a panel speaker with a waterproof function. That is, resin sheets with a waterproof function are provided for the front and back planes of an acoustic vibration plat to which a piezoelectric type acoustic driver is provided for a foaming resin board. Limb sections of the resin sheets with the waterproof function are fit to the resin frame which is provided around the acoustic vibration plate. The section shape of the resin frame has a gap section such as U-shaped or Z-shaped formation.
Therefore, an object of the present invention is to provide a panel speaker in which the dimensions of a space for storing a panel speaker can be minimized.
Another object of the present invention is to provide a panel speaker in which the panel speaker itself or an instrument using the panel speaker can be down-sized by changing the location of a vibration driver on an acoustic vibrating plate.
Still another object of the present invention is to provide a panel speaker which has an acoustic vibrating plate made of a transparent material and can be used in wide application fields of a panel speaker.
In order to achieve an aspect of the present invention, a panel speaker includes an acoustic vibrating plate, and a vibration driver mounted off a center of the acoustic vibrating plate and applying vibration to the acoustic vibrating plate.
The vibration driver is desirably located outside of a region defined by connecting intermediate points of lines extending between the center of the acoustic vibrating plate and edges of the acoustic vibrating plate. In this case, the vibration driver is more desirably located at or adjacent to an edge portion of the acoustic vibrating plate. The acoustic vibrating plate may be formed to have substantially a rectangular shape, and the vibration driver is located at or adjacent to a corner of the acoustic vibrating plate.
The direction of application of the vibration by the vibration driver desirably may be a direction other than a direction perpendicular to a surface plane of the acoustic vibrating plate.
Also, the acoustic vibrating plate desirably has a transparent material film provided at least locally thereon to allow a background to be viewed. In addition, the acoustic vibrating plate may have a reflection preventing film provided at least locally thereon to prevent reflection of incoming light, or a light reflective film to reflect incoming light.
In order to achieve another aspect of the present invention, a panel speaker includes an acoustic vibrating plate, and a plurality of vibration drivers mounted outside of a region defined by connecting intermediate points of lines extending between a center of the acoustic vibrating plate and edges of the acoustic vibrating plate, and applying vibration on the acoustic vibrating plate.
Here, at least one of the plurality of vibration drivers is desirably located at or adjacent to an edge portion of the acoustic vibrating plate. When the acoustic vibrating plate is formed to have substantially a rectangular shape, the vibration driver may be located at or adjacent to one corner of the acoustic vibrating plate.
The direction of application of the vibration by the vibration driver may be a direction other than a direction perpendicular to a surface plane of the acoustic vibrating plate.
Also, an amplitude of the vibration applied by at least one of the plurality of vibration drivers may be different from an amplitude of the vibration applied by each of the remaining vibration drivers. The direction of the vibration applied by at least one of the plurality of vibration drivers may be different from a direction of the vibration applied by each of the remaining vibration drivers. In addition, the phase of the vibration applied by at least one of the plurality of vibration drivers may be different from a phase of the vibration applied by each of the remaining vibration drivers.
Also, the acoustic vibrating plate may have a transparent material film provided at least locally thereon to allow a background to be viewed, or have a reflection preventing film provided at least locally thereon to prevent reflection of incoming light, or a light reflective film to reflect incoming light.
In order to achieve still another aspect of the present invention, a panel speaker includes an acoustic vibrating plate, a plurality of vibration drivers mounted outside of a region defined by connecting intermediate points of lines extending between a center of the acoustic vibrating plate and edges of the acoustic vibrating plate and applying vibration on the acoustic vibrating plate, and a control unit controlling at lease one of the plurality of vibration drivers.
The control unit controls an amplitude of the vibration applied by the at least one vibration driver, or controls a phase of the vibration applied by the at least one vibration driver. Also, the control unit controls the plurality of vibration drivers to control propagation of vibration in the acoustic vibrating plate.
Also, the acoustic vibrating plate may have a transparent material film provided at least locally thereon to allow a background to be viewed, or have a reflection preventing film provided at least locally thereon to prevent reflection of incoming light, or a light reflective film to reflect incoming light.